Problem: Simplify the following expression: $k = \dfrac{a + 4}{5a} + \dfrac{-9a - 12}{5a}$
Solution: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{a + 4 - 9a - 12}{5a}$ Combine like terms: $k = \dfrac{-8a - 8}{5a}$